Rigorous biochemical analyses of pulmonary surfactant show that it is comprised of disaturated phosphatidylcholine, monoenoic phosphatidylcholine, phosphatidylglycerol, a unique apoprotein, and small amounts of neutral lipids, other phospholipids, and carbohydrate. The principal physiological function of pulmonary surfactant is well-known -- it lowers the surface tension of the alveolar interface to less than 15 dynes/cm. It has been determined that the disaturated phosphatidylcholine is capable of this process. Still unknown, however, are the physiological roles of the other lipids, and the apoprotein. This project will explore how the composition of these lipids may affect the physical properties of the entire complex, and how this may relate to respiratory mechanics. Significant emphasis will be given to the interaction of the apoprotien of surfactant with well-defined mixtures of lipids, and the effect of this interaction on the physical properties of the recombinant complex. An attempt will be made to find which of the lipid and/or protein constituents are needed to form tubular myelin, and to correlate morphologic structure with physicochemical properties.